1. Technical Field
The present invention relates to a media separation roller installing mechanism that installs a media separation roller for separating multifed sheet media to a position opposing a media conveyance roller. The invention also relates to a roller holder unit including the media separation roller installing mechanism. The invention further relates to a media conveyance device and a printer having the media separation roller installing mechanism.
2. Related Art
Devices having a media separation roller as a media separation mechanism to prevent multifeeding sheet media such as printing paper are known from the literature. The media separation roller is generally called a retard roller, and a mechanism having this roller is called a retard separation mechanism. When recording media are fed to the nipping point between the feed roller and the retard roller in this retard separation mechanism, the medium is advanced by the paper feed roller while a heavy feed load is applied to the media by friction from the retard roller. The retard roller deteriorates over time, including a drop in the media separation force due to wear. As a result, the retard roller is installed in the printer or other apparatus so that the retard roller can be replaced.
JP-A-H06-191670 and JP-A-2012-071918 disclose a sheet feeding device and a recording mechanism that have a replaceable retard roller. The sheet feeding device taught in JP-A-H06-191670 fastens the retard roller installation member to the device with screws, and the retard roller can be replaced by removing the screws. The recording device taught in JP-A-2012-071918 enables sliding the retard roller along the roller axis. To remove the retard roller from the paper path, the retard roller is slid from a fixed operating position to a replacement position.
The retard roller replacement mechanism taught in JP-A-H06-191670 requires using a tool such as a screwdriver to replace the retard roller. Replacing the retard roller is therefore not simple. The retard roller replacement mechanism taught in JP-A-JP-A-2012-071918 requires sliding the retard roller along the roller shaft in order to replace the retard roller. This requires providing a slide mechanism for sliding the retard roller from the fixed position to the replacement position, and space sufficient to slide the retard roller, inside the paper path. This inhibits reducing the overall size of the apparatus.
The retard roller is also assembled so that it is pushed with a specific amount of pressure to the conveyance roller or the paper feed roller by a spring or other urging member. To replace the retard roller, the retard roller must be separated from the conveyance roller or paper feed roller in resistance to this pressure, and the retard roller removed while this pressure is relieved. Replacing the retard roller is therefore not easy because the retard roller must be removed and installed while pressure is applied.